1. Field of the Invention
The present invention relates to illumination optics and a projection display apparatus for causing a display apparatus to illuminate and, in particular, to illumination optics and a projection display apparatus comprising integrator optics having two fly-eye lenses.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2003-337378 and Japanese Patent Laid-Open No. 2004-326101, for example, disclose integrator optics having two fly-eye lenses having lens elements as illustrated in FIG. 1 aligned in order.
In the description on general configuration, this type of optics comprises first fly-eye lens 1101 having a plurality of similarly-figured lens elements resembling an object for illumination in order to illuminate display apparatus 1107 shown in FIG. 1 such as an LCD with light coming out of light source (a lamp) not shown in the drawing, and second fly-eye lens 1102 with light of respective lens elements coming out of first fly-eye lens 1101 which is superimposed to form images on an object to be illuminated.
Light coming out of respective lens elements of second fly-eye lens 1102 passes polarization conversion element 1103, is aligned to provide single directional polarized light such as s-polarized light or p-polarized light, thereafter passes first field lens 1104 and second field lens 1105 and passes polarization plate 1106 to illuminate a range wider than display area 1108 that displays an image of display apparatus 1107.
Emission distribution of a lamp is not uniform over the bright center portion and the darker periphery. Therefore, that illumination distribution undergoes discretization with first fly-eye lens 1101. The discretized light enters second fly-eye lens 1102. Accordingly, light coming out of respective lens elements of second fly-eye lens 1102 differs in the brightness of illumination areas respectively.
Therefore, optical axis of a lens element is deflected so that illumination areas of light emitted out of respective lens elements of second fly-eye lens 1102 are positioned at the same place and the respective illumination regions are superimposed at the same region. That enables light having uniform illumination distribution of brightness to be irradiated onto a display area.
FIG. 2 illustrates a configuration for controlling an illumination area with the above described deflection.
FIG. 2A is a plan view illustrating the incident plane of second fly-eye lens 1102.
FIG. 2B illustrates an illumination area in the case where the center of the individual lens of first fly-eye lens 1101 corresponds with the center of the individual lens of second fly-eye lens 1102 at optical axis C. Each lens configuring respective fly-eye lens illustrated in FIG. 2A is in the state illustrated in FIG. 2B and then illumination areas having light emitted out from respective lens element of second fly-eye lens 1102 will provide respectively different regions in which uniform illumination light is lost.
In order to provide uniform illumination light, the lens at the diagonally-lined site in FIG. 2A of second fly-eye lens 1102 is in a deflected state with the lens center in a location deviated from optical axis C as illustrated in FIG. 2C. Thereby, the illumination area moves. The amount of deflection of the respective lens, that corresponds with the location in the incident plane, will differ so that the illumination area having light that comes out of the respective lens element of second fly-eye lens 1102 will occupy the same position as illustrated in FIG. 1.
As described above, the light coming out of the second fly-eye lens is configured to irradiate a range wider than the display area of an object for illumination. That is intended to cope with dispersion in optical axis adjustment on illumination optics during production and to cope with optical axis displacement due to impacts and the like when used after production.
In the case where dispersion in optical axis adjustment and impact cause the displacement of the optical axis to differ from design values, the illumination light that is emitted from the second fly-eye lens illuminates a display element at a location that departs from the designed location so as, in the worst case, not to illuminate any display area, or to cause display of a partial video in case where a projection display apparatus is configured.
In order to prevent such an occurrence, the light coming out of the second fly-eye lens irradiates a range wider than the display area of the object for illumination. That is, the illumination area is provided with a marginal portion that is to be illuminated. The light illuminated onto that marginal portion will not contribute to illuminating the projection image in the case where no optical axis displacement occurs. Conventionally, each lens configuring the second fly-eye lens is configured to illuminate the same region including the marginal portion. Therefore, brightness of the marginal portion originally not contributing to the projection image provides with the same brightness as the display area, thus acting to hamper improvement in optical utilization efficiency (improvement in brightness).
On the other hand, the second fly-eye lens is designed so that a uniform illumination area is obtainable by causing deflection of the respective optical axis of a plurality of component lens elements to cause the same illumination area to undergo irradiation. Respective optical axes of lens elements configuring the second fly-eye lens may deviate from the designed values in the level of deflection during manufacturing steps. Then only irradiation areas that are irradiated with illumination light from those lens elements are deflected. Consequently, there will be a portion that will have decreased brightness in the area that originally required illumination.
A phenomenon called a shadow in which light is not uniformly and evenly dispersed appears in the portion that is subject to a decrease in brightness, as described above. That shadow will become more pronounced as the other illumination areas become more uniform.
In order to prevent the above described shadow from appearing, it is necessary to limit deviation of the amount of deflection of the respective optical axes of the lens elements that configure the second fly-eye lens during manufacturing so that illumination areas having the same size are superimposed on the same location, and this requires extremely high technological capability. Consequently, management of production quality becomes difficult, resulting in higher costs.
In addition, the area which an individual focuses upon, when looking at a projected image, is the center portion of the display where many important videos are projected. Therefore a shadow that occurs in the center will become highly pronounced compared with a shadow that occurs at the edges. Moreover, important parts of videos are frequently displayed in the central portion of the video window, and it is therefore desirable that this central portion be brighter than the periphery. However, in the case of a configuration with respective lenses configure the second fly-eye lens to irradiate the same region, there is the probability that a shadow will be generated and that a uniform brightness will occur throughout all of the regions so that there will not be a irradiation state that correspond to the display area.